An unannounced train carrying over 1,000 asylum seekers, accompanied by around 40 Croatian police officers, has been intercepted by Hungarian authorities, who accused Zagreb of breaking international laws and intentionally participating in “human smuggling.”

The train carrying up to 1,000 refugees was accompanied by some 40 Croatian police officers, who were reportedly detained and then sent back. Croatian police however refuted initial reports that officers accompanying the train were detained or disarmed, explaining that 36 officers “returned” to Croatia in the evening.

“There was no disarming or arrests. It is not true,” Croatian police spokeswoman Jelena Bikic told Reuters, claiming that there was “an agreement about the escort between the police officers from the two sides in advance.”

Hungarian authorities said that the incident happened due to Croatia’s failure to coordinate train’s border crossing. According to the head of the Hungarian disaster unit, Gyorgy Bakondi, the Croatian train arrived at Magyarboly without any prior notice, bringing the number of unannounced arrivals to over 4,000 on Friday alone.

“The Croatian system for handling migrants and refugees has collapsed basically in one day,” Kovacs added. “What we see today is the failure of the Croatian state to handle migration issues. What is more we see intentional, intentional, participation in human smuggling taking the migrants to the Hungarian border.”

Hungary’s foreign minister earlier in the day accused Croatia of encouraging migrants to break the law.

“Rather than respecting the laws in place in the EU, they (Croatia), are encouraging the masses to break the law, because illegally crossing a border is breaking the law,” Peter Szijjarto said in Belgrade. “At the moment, the Croatian government is transporting migrants – in contravention of the laws in force in the European Union – towards the Hungarian border instead of giving them a place to stay and looking after their needs,” he added.

After Hungary blocked off their border with Serbia this week with the aid of a metal fence and riot police, migrants flooded neighboring Croatia in search for an alternative route. More than 17,000 have arrived in the country since Wednesday morning.

“We cannot register and accommodate these people any longer,” Croatian Prime Minister Zoran Milanovic told a news conference. “They will get food, water and medical help, and then they can move on. The European Union must know that Croatia will not become a migrant ‘hotspot’. We have hearts, but we also have heads.”

Meanwhile European Commission President Jean-Claude Juncker offered Croatia logistical and technical assistance to cope with the migrant flow during a conversation with Milanovic.

“Both stressed the need to enhance the protection of the EU's external border, to step up EU assistance in our immediate neighborhood and to make swift progress on operational solidarity between the EU Member States to cope with the refugee crisis,” Juncker's office said.